Current posterior spine implantation instrumentation devices utilize pedicle fixation to secure rods or plates to the posterior spine. Reference is made to FIG. 1, which shows the stabilization of two spinal levels, with the understanding that certain conditions, such as scoliosis, require immobilization and alignment of multiple levels. In the figure, the upper vertebral body is indicated at 102, with the lower vertebral body being indicated at 103. The disc between the bodies is shown as 108. The upper vertebral body 102 includes transverse processes 106, and spinous process 112. The superior articular processes 104 are shown with respect to the upper vertebral body, in the absence of an entire facet joint, though a completed joint is shown at 110 between the upper and lower bodies.
A typical prior-art plate/rod fixation system includes longitudinal members 120, 122 which are anchored via pedicle screws 124, 126. Often link members, such as 128, are utilized to offset the members 120, 122 into an appropriate region of the spine, on either side of the spinous processes. Rods having a circular cross-section are ordinarily used, though in this application, other geometries, including rectangular “plates” are common as well.
Various existing fixation systems utilize the facet joint as opposed to pedicle screw and rod/plate alignment. FIG. 2, for example, shows an existing translaminar fixation system, which utilizes some sort of a fastener 202, typically having a drive head 204. The fastener is oriented through the lamina on one side of the vertebral body, and down through the facet joint on the other side of the spinal column. The fastener, indicated at 202, is typically a threaded screw which is inserted following guide wire and pilot hole formation.
Also in the prior-art, is the use of facet fixation directly across a facet joint, as indicated in FIG. 3. Here, a fastener having a threaded portion 302 is driven through the joint, as shown, utilizing some sort of a proximal drive head 304. Approaches utilizing transfacet fixation are presently stand-alone devices, and are not linked together, or to pedicle screws via any rod/plate system.